Nonwoven Web Material Containing Crosslinked Elastic Component Formed from a Pentablock Copolymer

ABSTRACT

A nonwoven web material that includes an elastic component or material (e.g., nonwoven web, nonwoven web laminated to an elastic material, etc.) is provided. The elastic component contains a crosslinked network formed from a pentablock copolymer containing at least two monoalkenyl aromatic midblocks positioned between conjugated diene endblocks, such as butadiene-styrene-butadiene-styrene-butadiene (“BSBSB”) or isoprene-styrene-isoprene-styrene-isoprene (“ISISI”). Prior to crosslinking, the pentablock copolymers have a relatively low viscosity and thus may be readily formed into a precursor elastic material (e.g., film, strands, web, etc.) that is subsequently crosslinked to achieve the desired elastic and mechanical properties.

BACKGROUND OF THE INVENTION

Elastic films are commonly incorporated into products (e.g., diapers,training pants, garments, etc.) to improve their ability to better fitthe contours of the body. For example, an elastic composite may beformed from the elastic film and one or more nonwoven web facings. Thenonwoven web facing may be joined to the elastic film while the film isin a stretched condition so that the nonwoven web facing can gatherbetween the locations where it is bonded to the film when it is relaxed.The resulting elastic composite is stretchable to the extent that thenonwoven web facing gathered between the bond locations allows theelastic film to elongate. Styrenic block copolymers are often employedto form the elastic film of such composites that contain a conjugatedbutadiene block positioned between two styrene blocks (i.e., S-B-S).Unfortunately, such polymers are often difficult to process into a filmdue to their relatively high viscosity. As such, a need exists for amaterial that may be formed from a low viscosity polymer, yet exhibitgood elastic performance during use.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present invention, a nonwovenweb material is disclosed that comprises an elastic component thatincludes a crosslinked network. The crosslinked network contains apentablock copolymer having at least two monoalkenyl aromatic midblockspositioned between conjugated diene endblocks, such asbutadiene-styrene-butadiene-styrene-butadiene (“BSBSB”) and/orisoprene-styrene-isoprene-styrene-isoprene (“ISISI”).

Other features and aspects of the present invention are described inmore detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth more particularly in the remainder of the specification, whichmakes reference to the appended figures in which:

FIG. 1 is a schematic illustration of a method for forming a compositein accordance with one embodiment of the present invention; and

FIG. 2 is a perspective view of an absorbent article that may be formedin accordance with one embodiment of the present invention.

Repeat use of reference characters in the present specification anddrawings is intended to represent same or analogous features or elementsof the invention.

DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTS Definitions

As used herein, the term “absorbent article” generally refers to anyarticle capable of absorbing water or other fluids. Examples of someabsorbent articles include, but are not limited to, personal careabsorbent articles, such as diapers, training pants, absorbentunderpants, incontinence articles, feminine hygiene products (e.g.,sanitary napkins), swim wear, baby wipes, and so forth; medicalabsorbent articles, such as garments, fenestration materials, underpads,bedpads, bandages, absorbent drapes, and medical wipes; food servicewipers; clothing articles; and so forth. Materials and processessuitable for forming such absorbent articles are well known to thoseskilled in the art.

As used herein, the term “nonwoven web” generally refers to a web havinga structure of individual fibers or threads which are interlaid, but notin an identifiable manner as in a knitted fabric. Examples of suitablenonwoven fabrics or webs include, but are not limited to, meltblownwebs, spunbond webs, carded webs, etc. The basis weight of the nonwovenweb may generally vary, such as from about 0.1 grams per square meter(“gsm”) to 120 gsm, in some embodiments from about 0.5 gsm to about 70gsm, and in some embodiments, from about 1 gsm to about 35 gsm.

As used herein, the term “meltblown web” generally refers to a nonwovenweb that is formed by a process in which a molten thermoplastic materialis extruded through a plurality of fine, usually circular, diecapillaries as molten fibers into converging high velocity gas (e.g.air) streams that attenuate the fibers of molten thermoplastic materialto reduce their diameter, which may be to microfiber diameter.Thereafter, the meltblown fibers are carried by the high velocity gasstream and are deposited on a collecting surface to form a web ofrandomly dispersed meltblown fibers. Such a process is disclosed, forexample, in U.S. Pat. No. 3,849,241 to Butin, et al., which isincorporated herein in its entirety by reference thereto for allpurposes. Generally speaking, meltblown fibers may be microfibers thatare substantially continuous or discontinuous, generally smaller than 10microns in diameter, and generally tacky when deposited onto acollecting surface.

As used herein, the term “spunbond web” generally refers to a webcontaining small diameter substantially continuous fibers. The fibersare formed by extruding a molten thermoplastic material from a pluralityof fine, usually circular, capillaries of a spinnerette with thediameter of the extruded fibers then being rapidly reduced as by, forexample, eductive drawing and/or other well-known spunbondingmechanisms. The production of spunbond webs is described andillustrated, for example, in U.S. Pat. No. 4,340,563 to Appel, et al.,U.S. Pat. No. 3,692,618 to Dorschner, et al., U.S. Pat. No. 3,802,817 toMatsuki, et al., U.S. Pat. No. 3,338,992 to Kinney, U.S. Pat. No.3,341,394 to Kinney, U.S. Pat. No. 3,502,763 to Hartman, U.S. Pat. No.3,502,538 to Levy, U.S. Pat. No. 3,542,615 to Dobo, et al., and U.S.Pat. No. 5,382,400 to Pike, et al., which are incorporated herein intheir entirety by reference thereto for all purposes. Spunbond fibersare generally not tacky when they are deposited onto a collectingsurface. Spunbond fibers may sometimes have diameters less than about 40microns, and are often between about 5 to about 20 microns.

As used herein, the terms “machine direction” or “MD” generally refersto the direction in which a material is produced. The term“cross-machine direction” or “CD” refers to the direction perpendicularto the machine direction. Dimensions measured in the cross-machinedirection are referred to as “width” dimension, while dimensionsmeasured in the machine direction are referred to as “length”dimensions.

As used herein, the term “elastomeric” and “elastic” and refers to amaterial that, upon application of a stretching force, is stretchable ina direction (such as the MD or CD direction), and which upon release ofthe stretching force, contracts/returns to approximately its originaldimension. For example, a stretched material may have a stretched lengththat is at least 50% greater than its relaxed unstretched length, andwhich will recover to within at least 50% of its stretched length uponrelease of the stretching force. A hypothetical example would be a2.54-cm sample of a material that is stretchable to at least 3.81centimeters and which, upon release of the stretching force, willrecover to a length of not more than 3.175 centimeters. Desirably, thematerial contracts or recovers at least 50%, and even more desirably, atleast 80% of the stretched length.

As used herein the terms “extensible” or “extensibility” generallyrefers to a material that stretches or extends in the direction of anapplied force by at least about 50% of its relaxed length or width. Anextensible material does not necessarily have recovery properties. Forexample, an elastomeric material is an extensible material havingrecovery properties. A meltblown web may be extensible, but not haverecovery properties, and thus, be an extensible, non-elastic material.

As used herein, the term “percent stretch” refers to the degree to whicha material stretches in a given direction when subjected to a certainforce. In particular, percent stretch is determined by measuring theincrease in length of the material in the stretched dimension, dividingthat value by the original dimension of the material, and thenmultiplying by 100. Such measurements are determined using the “stripelongation test”, which is substantially in accordance with thespecifications of ASTM D5035-95. Specifically, the test uses two clamps,each having two jaws with each jaw having a facing in contact with thesample. The clamps hold the material in the same plane, usuallyvertically, separated by 3 inches (7.62 cm) and move apart at aspecified rate of extension. The sample size is 3 inches by 6 inches(7.62 cm×15.24 cm), with a jaw facing height of 1 inch (2.54 cm) andwidth of 3 inches (7.62 cm), and a constant rate of extension of 300mm/min. The specimen is clamped in, for example, a Sintech 2/S testerwith a Renew MTS mongoose box (control) and using TESTWORKS 4.07bsoftware (MTS Corp, of Minneapolis, Minn.). The test is conducted underambient conditions. Results are generally reported as an average ofthree specimens and may be performed with the specimen in the crossdirection (CD) and/or the machine direction (MD).

Detailed Description

Reference now will be made in detail to various embodiments of theinvention, one or more examples of which are set forth below. Eachexample is provided by way of explanation, not limitation of theinvention. In fact, it will be apparent to those skilled in the art thatvarious modifications and variations may be made in the presentinvention without departing from the scope or spirit of the invention.For instance, features illustrated or described as part of oneembodiment, may be used on another embodiment to yield a still furtherembodiment. Thus, it is intended that the present invention cover suchmodifications and variations.

Generally speaking, the present invention is directed to a nonwoven webmaterial that includes an elastic component or material (e.g., nonwovenweb, nonwoven web laminated to an elastic material, etc.). The elasticcomponent contains a crosslinked network formed from a pentablockcopolymer containing at least two monoalkenyl aromatic midblockspositioned between conjugated diene endblocks, such asbutadiene-styrene-butadiene-styrene-butadiene (“BSBSB”) and/orisoprene-styrene-isoprene-styrene-isoprene (“ISISI”). Such pentablockcopolymers may be formed using any known technique, such as sequentialpolymerization or through coupling, which may leave a residue of thecoupling agent in the polymer. Regardless, prior to crosslinking, thepentablock copolymers have a relatively low viscosity and thus may bereadily formed into a precursor elastic material (e.g., film, strands,web, etc.) that is subsequently crosslinked to achieve the desiredelastic and mechanical properties. Crosslinking is typically achievedthrough the formation of free radicals (unpaired electrons) that linktogether to form a plurality of carbon-carbon covalent bonds at theconjugated diene endblocks. The use of multiple conjugated dieneendblocks in the copolymer of the present invention thus provides agreater number of crosslinking sites than would otherwise be availableif, for example, the conjugated diene was a midblock of the copolymer(e.g., S-B-S copolymers). It is also believed that the uncrosslinkedpentablock polymer (e.g., pellets) may exhibit a relatively low amountof blocking and dusting during conversion and transportation incomparison to what is often experienced with conventional S-B-Scopolymers.

The monoalkenyl aromatic midblock may include styrene, as well asderivatives thereof, such as α-methylstyrene, p-methylstyrene,p-tert-butyl styrene, p-ethylstyrene, m-isopropylstyrene,p-hexylstyrene, α-methylstyrene, α,4-dimethylstyrene, 1,3dimethylstyrene p-methylstyrene; etc., as well as other monoalkenylpolycyclic aromatic compounds, such as vinyl naphthalene, vinylanthrycene; and so forth. Preferred monoalkenyl aromatics are styreneand p-methylstyrene. The conjugated diene endblocks may includehomopolymers of conjugated diene monomers, copolymers of two or moreconjugated dienes, and copolymers of one or more of the dienes withanother monomer in which the blocks are predominantly conjugated dieneunits. Preferably, the conjugated dienes contain from 4 to 8 carbonatoms, such as 1,3 butadiene (butadiene), 2-methyl-1,3 butadiene(isoprene), 2,3 dimethyl-1,3 butadiene, 1,3 pentadiene (piperylene), 1,3hexadiene, 2-methyl-1,3-hexadiene, 1,3-octadiene, or derivativesthereof. Of the conjugated dienes, butadiene and isoprene are preferred.

Any known polymerization technique may be employed to form thepentablock copolymers, such as sequential addition of monomertechniques, incremental addition of monomer techniques, couplingtechniques, and so forth. Exemplary techniques are described, forinstance, in U.S. Pat. No. 4,070,418 to Harpell; U.S. Pat. No. 5,863,978to Vosters; and U.S. Pat. No. 6,730,637 to Stewart, et al., all of whichare incorporated herein in their entirety by reference thereto for allpurposes. In one particular embodiment, the pentablock copolymer isproduced by sequential polymerization. By way of example, a conjugateddiene monomer may be initially polymerized using 1,2-polymerization or1,4-polymerization. In 1,2-polymerization, one carbon-carbon double bondof the conjugated diene is involved in the formation of the polymerchain, which then has pendant ethylenically unsaturated groups. In1,4-polymerization, both carbon-carbon double bonds are involved in theformation of the polymeric chain, which then includes ethylenicunsaturation. The term “vinyl content” refers to the fact that aconjugated diene is polymerized via 1,2-addition (in the case ofbutadiene—it would be 3,4-addition in the case of isoprene). Although apure “vinyl” group is formed only in the case of 1,2-additionpolymerization of 1,3-butadiene, the effects of 3,4-additionpolymerization of isoprene (and similar addition for other conjugateddienes) on the final properties of the block copolymer will be similar.The term “vinyl” refers to the presence of a pendant vinyl group on thepolymer chain. When referring to the use of butadiene as the conjugateddiene, it is preferred that about 5 to about 25 mol percent of thecondensed butadiene units in the conjugated diene polymer block have 1,2vinyl configuration as determined by proton NMR analysis.

Regardless, a monoalkenyl aromatic block is allowed to “grow” on theinitial block of the polymerized conjugated diene. Substantiallycomplete polymerization of the conjugated diene before thepolymerization of monoalkenyl aromatic results in the production ofrather discrete blocks. The product of the conjugated dienepolymerization is contacted, for example, with additional conjugateddiene to grow a second block of polymerized conjugated diene and producea living polymer of these five blocks (“pentablock copolymer”).Additional blocks may be introduced, if desired, by continuing thesequence. Subsequently, the living block polymer is contacted with anactive hydrogen compound (e.g., acid or an alcohol) to “kill” the livingpolymer and thereby terminate polymerization. Coupling agents of higherfunctionality may help produce block copolymers of a branchedconfiguration. For example, the use of a polyalkenyl coupling agent(e.g., divinylbenzene) may result in pentablock copolymers of a “star”configuration.

As indicated above, the resulting pentablock copolymer contains at leasttwo monoalkenyl aromatic midblocks positioned between conjugated dieneendblocks. The pentablock copolymer may be linear or branched and have avariety of different configurations as is known in the art. Forinstance, linear pentablock copolymers may be formed that have thegeneral structure “ABABA”, wherein “A” refers to a conjugated dieneblock (e.g., butadiene or isoprene, etc.) and “B” refers to amonoalkenyl aromatic block (e.g., styrene). Particularly suitablepolymers may include butadiene-styrene-butadiene-styrene-butadiene(“BSBSB”), isoprene-styrene-isoprene-styrene-isoprene (“ISISI”),butadiene-styrene-isoprene-styrene-butadiene (“BSISB”),butadiene-styrene-butadiene-styrene-isoprene (“BSBSI”),butadiene-styrene-isoprene-styrene-isoprene (“BSISI”),isoprene-styrene-butadiene-styrene-butadiene (“ISBSB”),isoprene-styrene-isoprene-styrene-butadiene (“ISISB”),isoprene-styrene-butadiene-styrene-isoprene (“ISBSI”), etc., andmixtures thereof.

In addition to a linear configuration, branched copolymers may also beemployed that have general structure “(A-B-A)_(n)”, wherein “A” and “B”are defined above and “n” represents the numbers of arms or chains andis equal to 2 or more, in some embodiments from 3 to about 30, and insome embodiments, from about 4 to about 8. Each arm may have arespective number average molecular weight of about 5,000 to about30,000, while the total molecular weight of the pentablock copolymer maystill fall within the ranges noted above. Such branched copoloymers mayprovide an even greater number of available crosslinking sites. Further,a greater portion of the styrene blocks may be contained within thecrosslinked network so that it contains fewer “dangling” styrene chainsthan conventional S-B-S block copolymers. This is desirable because thelarger dangling styrene blocks can sterically hinder crosslinking at theconjugated diene sites, thereby reducing elasticity. Thus, by possessinga greater number of crosslinking sites and fewer “dangling” styrenechains, the resulting three-dimensional network may likewise possessenhanced strength and elasticity.

A variety of characteristics of the pentablock copolymer may beselectively varied to achieve the desired properties of the elasticmaterial. For example, the pentablock copolymer may possess a molecularweight within an optimum range for processing. Namely, polymers havingtoo great of a molecular weight generally possess heavily entangledpolymer chains and thus result in a thermoplastic composition that isdifficult to process. Conversely, polymers having too low of a molecularweight do not generally possess enough entanglement, which leads to arelatively weak melt strength. Thus, the pentablock copolymer istypically formed to have a number average molecular weight (“M_(n)”)ranging from about 30,000 to about 250,000 grams per mole, in someembodiments from about 40,000 to about 200,000 grams per mole, in someembodiments from about 50,000 to about 150,000 grams per mole, and insome embodiments, from about 70,000 to about 110,000 grams per mole. Thenumber average molecular weight may be determined by methods known tothose skilled in the art. The molecular weight of each block may also becontrolled to influence the rheology, molecular weight, and thermalproperties of the copolymer. Monoalkenyl aromatic blocks with a lowermolecular weight, for instance, may result in copolymers with lowersoftening/melting points and molecular weights. However, too low of amolecular weight may adversely affect the strength of the resultingelastic material. Thus, each monoalkenyl aromatic block employed in thecopolymer may have a number average molecular weight (“M_(n)”) of fromabout 5,000 to about 35,000 grams per mole, in some embodiments fromabout 7,500 to about 30,000 grams per mole, and in some embodiments,from about 10,000 to about 25,000 grams per mole. Likewise, eachconjugated diene block employed in the copolymer may have a numberaverage molecular weight (“M_(n)”) ranging from about 20,000 to about150,000 grams per mole, in some embodiments from about 30,000 to about120,000 grams per mole, and in some embodiments, from about 40,000 toabout 100,000 grams per mole.

The relative amount of the blocks in the copolymer may also influencethe properties of the resulting elastic material. For example, highermonoalkenyl aromatic block concentrations may result in copolymers withlower melting points and molecular weights. However, too high of amonoalkenyl aromatic block concentration may not achieve the desiredstrength. Thus, the monoalkenyl aromatic block(s) typically constitutefrom about 1 wt. % to about 40 wt. %, in some embodiments from about 5wt. % to about 35 wt. %, and in some embodiments, from about 15 wt. % toabout 30 wt. % of the copolymer. Likewise, the conjugated diene blockstypically constitute from about 60 wt. % to about 99 wt. %, in someembodiments from about 65 wt. % to about 95 wt. %, and in someembodiments, from about 70 wt. % to about 85 wt. % of the copolymer.

To provide improved processability, the pentablock copolymer is alsoformed to have a “melt flow index” within a certain range. The melt flowindex is the weight of a polymer (in grams) that may be forced throughan extrusion rheometer orifice (0.0825-inch diameter) when subjected toa force of 2160 grams in 10 minutes at a certain temperature (e.g., 190°C. or 230° C.). More specifically, polymers having a low melt flowindex, or conversely a high viscosity, are generally difficult toprocess. Thus, in most embodiments, the melt flow index of thepentablock copolymer is high enough to provide a low viscosity polymer,such as at least about 1 gram per 10 minutes, in some embodiments atleast about 10 grams per 10 minutes, and in some embodiments, from about15 to about 500 grams per 10 minutes, measured in accordance with ASTMTest Method D1238-E at 190° C. Of course, the melt flow index of thecopolymer will ultimately depend upon the selected forming process.

If desired, the pentablock copolymer may also be subjected to selectivehydrogenation as is known in the art. More specifically, it is wellknown that pentablock copolymers may be hydrogenated under conditionsthat hydrogenate from about 80% to about 99% of the aliphaticunsaturation present in the pentablock copolymer, while hydrogenating nomore than 25%, and preferably no more than 5%, of the aromaticunsaturation of the polymer molecule. Conditions to effect suchhydrogenation, including the choice of a hydrogenation catalyst, areconventional and are well understood in the art. The resultingselectively hydrogenated pentablock copolymers may be identified by the“apparent” structure of the aliphatic block. For example, selectivehydrogenation of a butadiene-styrene-butadiene (“B-S-B-S-B”) polymerwill result in the production of a polymer having endblocks that are anapparent polyethylene in the case of conjugated diene blocks produced by1,4-polymerization and an apparent ethylene/butylene copolymer in thecase of conjugated diene blocks produced by predominantly1,2-polymerization. These selectively hydrogenated pentablock copolymersmay be designated E-S-E-S-E and EB-S-EB-S-EB, respectively. Likewise,the selective hydrogenation of an isoprene-styrene-isoprene(“I-S-I-S-I”) pentablock copolymer will result in the production of apolymer having endblocks that are an apparent ethylene/propylenecopolymer in the case of isoprene blocks produced by predominantly1,4-polymerization. Such hydrogenated pentablock copolymers may bedesignated EP-S-EP-S-EP.

Also suitable are functionalized derivatives of the above-describedpentablock copolymers. For example, suitable functional groups that maybe introduced into the pentablock copolymer molecule may includehydroxyl, epoxy, carboxyl or carboxylic acid anhydride functionalgroups. The introduction of such groups by further reaction of theinitially produced pentablock copolymers is conventional and well knownin the art. Of the functionalized pentablock copolymers, the preferredpolymers contain carboxyl functional groups illustratively produced byreaction of the initially produced, non-functionalized pentablockcopolymer with acrylic acid, methacrylic acid or maleic acid.

Regardless of its particular configuration, the low viscosity,monoalkenyl aromatic/conjugated diene pentablock copolymer of thepresent invention is incorporated into a precursor elastic material. Incontrast to conventional elastomeric block copolymers having arelatively high viscosity, the low viscosity pentablock copolymers ofthe present invention may be readily processed without difficulty. Theprecursor elastic material may be a film, foam, strands, nonwoven web,and so forth. In one embodiment, for example, the precursor elasticmaterial includes a film. Any known technique may be used to form afilm, including blowing, casting, flat die extruding, etc. In oneparticular embodiment, the film may be formed by a blown process inwhich a gas (e.g., air) is used to expand a bubble of a melt extrudedpolymer through an annular die. The bubble is then collapsed andcollected in flat film form. Processes for producing blown films aredescribed, for instance, in U.S. Pat. No. 3,354,506 to Raley; U.S. Pat.No. 3,650,649 to Schippers; and U.S. Pat. No. 3,801,429 to Schrenk etal., as well as U.S. Patent Application Publication Nos. 2005/0245162 toMcCormack, et al. and 2003/0068951 to Boggs, et al., all of which areincorporated herein in their entirety by reference thereto for allpurposes. Although not required, the film may be stretched to improveits properties. For example, the film may be drawn by rolls rotating atdifferent speeds of rotation so that the sheet is stretched to thedesired draw ratio in the longitudinal direction (machine direction). Inaddition, the uniaxially stretched film may also be oriented in thecross-machine direction to form a “biaxially stretched” film. Forexample, the film may be clamped at its lateral edges by chain clips andconveyed into a tenter oven. In the tenter oven, the film may be drawnin the cross-machine direction to the desired draw ratio by chain clipsdiverged in their forward travel. Various parameters of a stretchingoperation may be selectively controlled, including the draw ratio,stretching temperature, and so forth. In some embodiments, for example,the film is stretched in the machine direction at a stretch ratio offrom about 1.5 to about 7.0, in some embodiments from about 1.8 to about5.0, and in some embodiments, from about 2.0 to about 4.5. The stretchratio may be determined by dividing the length of the stretched film byits length before stretching. The stretch ratio may also beapproximately the same as the draw ratio, which may be determined bydividing the linear speed of the film upon stretching (e.g., speed ofthe nip rolls) by the linear speed at which the film is formed (e.g.,speed of casting rolls or blown nip rolls). The film may be stretched ata temperature from about 15° C. to about 50° C., in some embodimentsfrom about 25° C. to about 40° C., and in some embodiments, from about30° C. to about 40° C. Preferably, the film is “cold drawn”, i.e.,stretched without the application of external heat (e.g., heated rolls).

The film may be a mono- or multi-layered film. Multilayer films may beprepared by co-extrusion of the layers, extrusion coating, or by anyconventional layering process. Such multilayer films normally contain abase layer and skin layer, but may contain any number of layers desired.For example, the multilayer film may be formed from a base layer and oneor more skin layers, wherein the base layer is formed from a pentablockcopolymer in accordance with the present invention. In such embodiments,the skin layer(s) may be formed from any film-forming polymer. Ifdesired, the skin layer(s) may contain a softer, lower melting polymeror polymer blend that renders the layer(s) more suitable as heat sealbonding layers for thermally bonding the film to a nonwoven web facing.In most embodiments, the skin layer(s) are formed from an olefinpolymer. Additional film-forming polymers that may be suitable for usewith the present invention, alone or in combination with other polymers,include ethylene vinyl acetate, ethylene ethyl acrylate, ethyleneacrylic acid, ethylene methyl acrylate, ethylene normal butyl acrylate,nylon, ethylene vinyl alcohol, polystyrene, polyurethane, and so forth.

In another embodiment of the present invention, the precursor elasticmaterial includes a plurality of strands. The number of strands may varyas desired, such as from 5 to about 20, in some embodiments from about 7to about 18, and in some embodiments, from about 8 to 15 strands percross-directional inch. The strands may have a circular cross-section,but may alternatively have other cross-sectional geometries such aselliptical, rectangular as in ribbon-like strands, triangular,multi-lobal, etc. The diameter of the strands (the widestcross-sectional dimension) may vary as desired, such as within a rangeof from 0.1 to about 4 millimeters, in some embodiments from about 0.2to about 2.5 millimeters, and in some embodiments, from 0.5 to about 2millimeters. Further, the strands may generally be arranged in anydirection or pattern. For example, in one embodiment, the strands arearranged in a direction that is substantially parallel to the machinedirection and are desirably spaced apart from each other across thecross machine direction at similar intervals. The strands may besubstantially continuous in length so that they are in the form offilaments. Such filaments may be produced using any of a variety ofknown techniques, such as by melt extruding a polymer from a die havinga series of extrusion capillaries arranged in a row. As is well known inthe art, meltblown dies may be suitable for forming the filaments,except that the high velocity gas streams used in fiber attenuation aregenerally not employed. Rather, the molten polymer extrudate is pumpedfrom the die capillaries and allowed to extend away from the die underthe impetus of gravity.

If desired, a layer of the aforementioned strands may also be laminatedto an additional layer (e.g., meltblown web) to help secure the strandsto a facing so that they are less likely to loosen during use. Examplesof such laminates are described in more detail, for instance, in U.S.Pat. No. 5,385,775 to Wright and U.S. Patent Application Publication No.2005/0170729 to Stadelman, et al., which are incorporated herein intheir entirety by reference thereto for all purposes. In one embodiment,the strands contain the pentablock copolymer of the present inventionand the meltblown web contains a polyolefin.

Regardless of the particular form of the precursor elastic material, thepentablock copolymer of the present invention is typically employed inan amount of about 10 wt. % or more, in some embodiments about 25 wt. %or more, in some embodiments about 50 wt. % or more, in some embodimentsabout 75 wt. % or more, and in some embodiments, from about 75 wt. % toabout 95 wt. % of the polymer content of the material. Of course, otherpolymers may also be employed in the elastic material. When employed,the additional polymer(s) typically constitute from about 0.5 to about90 wt. %, in some embodiments from about 0.75 to about 75 wt. %, in someembodiments from about 1 wt. % to about 50 wt. %, in some embodimentsfrom about 2 wt. % to about 40 wt. %, and in some embodiments, fromabout 5 wt. % to about 25 wt. % of the precursor elastic material.

In one embodiment, for example, an additional thermoplastic elastomermay be employed to improve the elastic performance of the resultingelastic material. Any of a variety of thermoplastic elastomers maygenerally be employed, such as elastomeric polyesters, elastomericpolyurethanes, elastomeric polyamides, elastomeric copolymers, and soforth. For example, the thermoplastic elastomer may be a block copolymerhaving blocks of a monoalkenyl arene polymer separated by a block of aconjugated diene polymer. Contrary to the pentablock copolymers of thepresent invention, such block copolymers have a relatively highviscosity and are generally elastic in nature, even prior tocrosslinking. Particularly suitable thermoplastic elastomers areavailable from Kraton Polymers LLC of Houston, Tex. under the trade nameKRATON®. KRATON® polymers include styrene-diene block copolymers, suchas styrene-butadiene, styrene-isoprene, styrene-butadiene-styrene, andstyrene-isoprene-styrene. KRATON® polymers also include styrene-olefinblock copolymers formed by selective hydrogenation of styrene-dieneblock copolymers. Examples of such styrene-olefin block copolymersinclude styrene-(ethylene-butylene), styrene-(ethylene-propylene),styrene-(ethylene-butylene)-styrene,styrene-(ethylene-propylene)-styrene,styrene-(ethylene-butylene)-styrene-(ethylene-butylene),styrene-(ethylene-propylene)-styrene-(ethylene-propylene), andstyrene-ethylene-(ethylene-propylene)-styrene. Specific KRATON® blockcopolymers include those sold under the brand names G 1652, G 1657, andG 1730. Various suitable styrenic block copolymers are described in U.S.Pat. Nos. 4,663,220, 4,323,534, 4,834,738, 5,093,422 and 5,304,599,which are hereby incorporated in their entirety by reference thereto forall purposes. Other commercially available block copolymers include theS-EP-S elastomeric copolymers available from Kuraray Company, Ltd. ofOkayama, Japan, under the trade designation SEPTON®. Still othersuitable copolymers include the S-I-S and S-B-S elastomeric copolymersavailable from Dexco Polymers, LP of Houston, Tex. under the tradedesignation VECTOR™. Also suitable are polymers composed of an A-B-A-Btetrablock copolymer, such as discussed in U.S. Pat. No. 5,332,613 toTaylor, et al., which is incorporated herein in its entirety byreference thereto for all purposes. An example of such a tetrablockcopolymer is astyrene-poly(ethylene-propylene)-styrene-poly(ethylene-propylene)(“S-EP-S-EP”) block copolymer.

Other exemplary thermoplastic elastomers that may be used includepolyurethane elastomeric materials such as, for example, those availableunder the trademark ESTANE from Noveon, polyamide elastomeric materialssuch as, for example, those available under the trademark PEBAX(polyether amide) from Atofina Chemicals Inc., of Philadelphia, Pa., andpolyester elastomeric materials such as, for example, those availableunder the trade designation HYTREL from E.I. DuPont De Nemours &Company.

Furthermore, the precursor elastic material of the present invention mayalso contain a polyolefin, such as polyethylene, polypropylene, blendsand copolymers thereof. In one particular embodiment, a polyethylene isemployed that is a copolymer of ethylene or propylene and an α-olefin,such as a C₃-C₂₀ α-olefin or C₃-C₁₂ α-olefin. Suitable α-olefins may belinear or branched (e.g., one or more C₁-C₃ alkyl branches, or an arylgroup). Specific examples include 1-butene; 3-methyl-1-butene;3,3-dimethyl-1-butene; 1-pentene; 1-pentene with one or more methyl,ethyl or propyl substituents; 1-hexene with one or more methyl, ethyl orpropyl substituents; 1-heptene with one or more methyl, ethyl or propylsubstituents; 1-octene with one or more methyl, ethyl or propylsubstituents; 1-nonene with one or more methyl, ethyl or propylsubstituents; ethyl, methyl or dimethyl-substituted 1-decene;1-dodecene; and styrene. Particularly desired α-olefin comonomers are1-butene, 1-hexene and 1-octene. The ethylene or propylene content ofsuch copolymers may be from about 60 mole % to about 99 mole %, in someembodiments from about 80 mole % to about 98.5 mole %, and in someembodiments, from about 87 mole % to about 97.5 mole %. The α-olefincontent may likewise range from about 1 mole % to about 40 mole %, insome embodiments from about 1.5 mole % to about 15 mole %, and in someembodiments, from about 2.5 mole % to about 13 mole %.

The density of a linear olefin copolymer is a function of both thelength and amount of the α-olefin. That is, the greater the length ofthe α-olefin and the greater the amount of α-olefin present, the lowerthe density of the copolymer. Although not necessarily required, linear“plastomers” are particularly desirable in that the content of α-olefinshort chain branching content is such that the copolymer exhibits bothplastic and elastomeric characteristics—i.e., a “plastomer.” Becausepolymerization with α-olefin comonomers decreases crystallinity anddensity, the resulting plastomer normally has a density lower than thatof thermoplastic polymers (e.g., LLDPE), but approaching and/oroverlapping that of an elastomer. For example, the density of theplastomer may be about 0.91 grams per cubic centimeter (g/cm³) or less,in some embodiments from about 0.85 to about 0.89 g/cm³, and in someembodiments, from about 0.85 g/cm³ to about 0.88 g/cm³. Despite having adensity similar to elastomers, plastomers generally exhibit a higherdegree of crystallinity, are relatively non-tacky, and may be formedinto pellets that are non-adhesive and relatively free flowing.

Any of a variety of known techniques may generally be employed to formsuch polyolefins. For instance, olefin polymers may be formed using afree radical or a coordination catalyst (e.g., Ziegler-Natta).Preferably, the olefin polymer is formed from a single-site coordinationcatalyst, such as a metallocene catalyst. Such a catalyst systemproduces ethylene copolymers in which the comonomer is randomlydistributed within a molecular chain and uniformly distributed acrossthe different molecular weight fractions. Metallocene-catalyzedpolyolefins are described, for instance, in U.S. Pat. No. 5,571,619 toMcAlpin et al.; U.S. Pat. No. 5,322,728 to Davis et al.; U.S. Pat. No.5,472,775 to Obijeski et al.; U.S. Pat. No. 5,272,236 to Lai et al.; andU.S. Pat. No. 6,090,325 to Wheat. et al., which are incorporated hereinin their entirety by reference thereto for all purposes.

Particularly suitable plastomers for use in the present invention mayinclude ethylene-based copolymer plastomers available under the EXACT™from ExxonMobil Chemical Company of Houston, Tex. Other suitablepolyethylene plastomers are available under the designation ENGAGE™ andAFFINITY™ from Dow Chemical Company of Midland, Mich. Still othersuitable ethylene polymers are available from The Dow Chemical Companyunder the designations DOWLEX™ (LLDPE) and ATTANE™ (ULDPE). Othersuitable ethylene polymers are described in U.S. Pat. No. 4,937,299 toEwen et al.; U.S. Pat. No. 5,218,071 to Tsutsui et al.; U.S. Pat. No.5,272,236 to Lai, et al.; and U.S. Pat. No. 5,278,272 to Lai, et al.,which are incorporated herein in their entirety by reference thereto forall purposes. Suitable propylene-based plastomers are likewisecommercially available under the designations VISTAMAXX™ from ExxonMobilChemical Co. of Houston, Tex.; FINA™ (e.g., 8573) from Atofina Chemicalsof Feluy, Belgium; TAFMER™ available from Mitsui PetrochemicalIndustries; and VERSIFY™ available from Dow Chemical Co. of Midland,Mich. Other examples of suitable propylene polymers are described inU.S. Pat. No. 6,500,563 to Datta, et al.; U.S. Pat. No. 5,539,056 toYang, et al.; and U.S. Pat. No. 5,596,052 to Resconi, et al., which areincorporated herein in their entirety by reference thereto for allpurposes.

Besides polymers, the precursor elastic material of the presentinvention may also contain other components as is known in the art. Inone embodiment, for example, the film contains a filler. Fillers areparticulates or other forms of material that may be added to the filmpolymer extrusion blend and that will not chemically interfere with theextruded film, but which may be uniformly dispersed throughout the film.Fillers may serve a variety of purposes, including enhancing filmopacity and/or breathability (i.e., vapor-permeable and substantiallyliquid-impermeable). For instance, filled films may be made breathableby stretching, which causes the polymer to break away from the fillerand create microporous passageways. Breathable microporous elastic filmsare described, for example, in U.S. Pat. Nos. 5,997,981; 6,015,764; and6,111,163 to McCormack, et al.; U.S. Pat. No. 5,932,497 to Morman, etal.; U.S. Pat. No. 6,461,457 to Taylor, et al., which are incorporatedherein in their entirety by reference thereto for all purposes.

The fillers may have a spherical or non-spherical shape with averageparticle sizes in the range of from about 0.1 to about 7 microns.Examples of suitable fillers include, but are not limited to, calciumcarbonate, various kinds of clay, silica, alumina, barium carbonate,sodium carbonate, magnesium carbonate, talc, barium sulfate, magnesiumsulfate, aluminum sulfate, titanium dioxide, zeolites, cellulose-typepowders, kaolin, mica, carbon, calcium oxide, magnesium oxide, aluminumhydroxide, pulp powder, wood powder, cellulose derivatives, chitin andchitin derivatives. A suitable coating, such as stearic acid, may alsobe applied to the filler particles if desired. When utilized, the fillercontent may vary, such as from about 25 wt. % to about 75 wt. %, in someembodiments, from about 30 wt. % to about 70 wt. %, and in someembodiments, from about 40 wt. % to about 60 wt. % of the film.

Other additives may also be incorporated into the precursor elasticmaterial, such as crosslinking catalysts, pro-rad additives, meltstabilizers, processing stabilizers, heat stabilizers, lightstabilizers, antioxidants, heat aging stabilizers, whitening agents,antiblocking agents, bonding agents, tackifiers, viscosity modifiers,etc. Suitable crosslinking catalysts, for instance, may include organicbases, carboxylic acids, and organometallic compounds, such as organictitanates and complexes or carboxylates of lead, cobalt, iron, nickel,zinc and tin (e.g., dibutyltindilaurate, dioctyltinmaleate,dibutyltindiacetate, dibutyltindioctoate, stannous acetate, stannousoctoate, lead naphthenate, zinc caprylate, cobalt naphthenate; etc.).Suitable pro-rad additives may likewise include azo compounds, organicperoxides and polyfunctional vinyl or allyl compounds such as, triallylcyanurate, triallyl isocyanurate, pentaerthritol tetramethacrylate,glutaraldehyde, polyester acrylate oligomers (e.g., available fromSartomer under the designation CN2303), ethylene glycol dimethacrylate,diallvl maleate, dipropargyl maleate, dipropargyl monoallyl cyanurate,dicumyl peroxide, di-tert-butyl peroxide, t-butyl perbenzoate, benzoylperoxide, cumene hydroperoxide, t-butyl peroctoate, methyl ethyl ketoneperoxide, 2,5-dimethyl-2,5-di(t-butyl peroxy)hexane, lauryl peroxide,tert-butyl peracetate, azobisisobutyl nitrite, etc.

Examples of suitable tackifiers may include, for instance, hydrogenatedhydrocarbon resins. REGALREZ™ hydrocarbon resins are examples of suchhydrogenated hydrocarbon resins, and are available from EastmanChemical. Other tackifiers are available from ExxonMobil under theESCOREZ™ designation. Viscosity modifiers may also be employed, such aspolyethylene wax (e.g., EPOLENE™ C-10 from Eastman Chemical). Phosphitestabilizers (e.g., IRGAFOS available from Ciba Specialty Chemicals ofTerrytown, N.Y. and DOVERPHOS available from Dover Chemical Corp. ofDover, Ohio) are exemplary melt stabilizers. In addition, hindered aminestabilizers (e.g., CHIMASSORB available from Ciba Specialty Chemicals)are exemplary heat and light stabilizers. Further, hindered phenols arecommonly used as an antioxidant in the production of films. Somesuitable hindered phenols include those available from Ciba SpecialtyChemicals of under the trade name “Irganox®”, such as Irganox® 1076,1010, or E 201. Moreover, bonding agents may also be added to the filmto facilitate bonding to additional materials (e.g., nonwoven web). Whenemployed, such additives (e.g., tackifier, antioxidant, stabilizer,crosslinking agents, pro-rad additives, etc.) may each be present in anamount from about 0.001 wt. % to about 25 wt. %, in some embodiments,from about 0.005 wt. % to about 20 wt. %, and in some embodiments, from0.01 wt. % to about 15 wt. % of the elastic material.

The pentablock copolymer of the present invention may be crosslinkedafter it is incorporated into the precursor elastic material to providethe polymer and material with elastic characteristics. Crosslinking maybe achieved through the formation of free radicals (unpaired electrons)that link together to form a plurality of carbon-carbon covalent bonds.Free radical formation may be accomplished in a variety of ways, such asthrough electromagnetic radiation, either alone or in the presence ofpro-rad additives, such as described above. More specifically,crosslinking may be induced by subjecting the precursor elastic materialto electromagnetic radiation. Some suitable examples of electromagneticradiation that may be used in the present invention include, but are notlimited to, ultraviolet light, electron beam radiation, natural andartificial radio isotopes (e.g., α, β, and γ rays), x-rays, neutronbeams, positively-charged beams, laser beams, and so forth. Electronbeam radiation, for instance, involves the production of acceleratedelectrons by an electron beam device. Electron beam devices aregenerally well known in the art. For instance, in one embodiment, anelectron beam device may be used that is available from Energy Sciences,Inc., of Woburn, Mass. under the name “Microbeam LV.” Other examples ofsuitable electron beam devices are described in U.S. Pat. No. 5,003,178to Livesay; U.S. Pat. No. 5,962,995 to Avnery; U.S. Pat. No. 6,407,492to Avnery, et al., which are incorporated herein in their entirety byreference thereto for all purposes.

When supplying electromagnetic radiation, it is generally desired toselectively control various parameters of the radiation to enhance thedegree of crosslinking. For example, one parameter that may becontrolled is the wavelength λ of the electromagnetic radiation.Specifically, the wavelength λ of the electromagnetic radiation variesfor different types of radiation of the electromagnetic radiationspectrum. Although not required, the wavelength λ of the electromagneticradiation used in the present invention is generally about 1000nanometers or less, in some embodiments about 100 nanometers or less,and in some embodiments, about 1 nanometer or less. Electron beamradiation, for instance, typically has a wavelength λ of about 1nanometer or less. Besides selecting the particular wavelength λ of theelectromagnetic radiation, other parameters may also be selected tooptimize the degree of crosslinking. For example, higher dosage andenergy levels of radiation will typically result in a higher degree ofcrosslinking; however, it is generally desired that the materials not be“overexposed” to radiation. Such overexposure may result in an unwantedlevel of product degradation. Thus, in some embodiments, the totaldosage employed (in one or multiple steps) may range from about 1megarad (Mrad) to about 30 Mrads, in some embodiments, from about 3Mrads to about 25 Mrads, and in some embodiments, from about 5 to about15 Mrads. In addition, the energy level may range from about 0.05megaelectron volts (MeV) to about 600 MeV.

It should be understood, however, that the actual dosage and/or energylevel required depends on the type of polymers and electromagneticradiation. Specifically, certain types of polymers may tend to form alesser or greater number of crosslinks, which will influence the dosageand energy of the radiation utilized. Likewise, certain types ofelectromagnetic radiation may be less effective in crosslinking thepolymer, and thus may be utilized at a higher dosage and/or energylevel. For instance, electromagnetic radiation that has a relativelyhigh wavelength (lower frequency) may be less efficient in crosslinkingthe polymer than electromagnetic radiation having a relatively lowwavelength (higher frequency). Accordingly, in such instances, thedesired dosage and/or energy level may be increased to achieve thedesired degree of crosslinking.

Upon crosslinking, a three-dimensional crosslinked network is formedthat provides the material with elasticity in the machine direction,cross-machine direction, or both. In addition to forming athree-dimensional elastomer network, crosslinking may also provide avariety of other benefits. Lotions used to enhance skin care, forinstance, may contain petroleum-based components and/or other componentsthat are compatible with thermoplastics polymers. If the lotions comeinto sufficient contact with an elastic material, its performance may besignificantly degraded. In this regard, the crosslinked pentablockcopolymers may exhibit improvement in lotion degradation resistance.Furthermore, certain types of crosslinking techniques (e.g., electronbeam radiation) may generate sufficient heat to effectively “heatshrink” the elastic material and provide it with additional latentstretchability. A separate heat activation step may also be employed tofurther enhance the heat shrinkage performance of the elastic material.Such an additional heat activation step may occur before and/or aftercrosslinking.

As stated above, the elastic material may be incorporated into anonwoven web material. This may be accomplished by blending the elasticcomponent with other fiber-forming materials (e.g., polypropylene).Alternatively, one or more nonwoven web facings may also be laminated tothe elastic material to reduce the coefficient of friction and enhancethe cloth-like feel of its surface. The basis weight of the nonwoven webfacing may generally vary, such as from about 5 grams per square meter(“gsm”) to 120 gsm, in some embodiments from about 8 gsm to about 70gsm, and in some embodiments, from about 10 gsm to about 35 gsm. Whenmultiple nonwoven web facings, such materials may have the same ordifferent basis weights.

Exemplary polymers for use in forming nonwoven web facings may include,for instance, polyolefins, e.g., polyethylene, polypropylene,polybutylene, etc.; polytetrafluoroethylene; polyesters, e.g.,polyethylene terephthalate and so forth; polyvinyl acetate; polyvinylchloride acetate; polyvinyl butyral; acrylic resins, e.g., polyacrylate,polymethylacrylate, polymethylmethacrylate, and so forth; polyamides,e.g., nylon; polyvinyl chloride; polyvinylidene chloride; polystyrene;polyvinyl alcohol; polyurethanes; polylactic acid; copolymers thereof;and so forth. If desired, biodegradable polymers, such as thosedescribed above, may also be employed. Synthetic or natural cellulosicpolymers may also be used, including but not limited to, cellulosicesters; cellulosic ethers; cellulosic nitrates; cellulosic acetates;cellulosic acetate butyrates; ethyl cellulose; regenerated celluloses,such as viscose, rayon, and so forth. It should be noted that thepolymer(s) may also contain other additives, such as processing aids ortreatment compositions to impart desired properties to the fibers,residual amounts of solvents, pigments or colorants, and so forth.

Monocomponent and/or multicomponent fibers may be used to form thenonwoven web facing. Monocomponent fibers are generally formed from apolymer or blend of polymers extruded from a single extruder.Multicomponent fibers are generally formed from two or more polymers(e.g., bicomponent fibers) extruded from separate extruders. Thepolymers may be arranged in substantially constantly positioned distinctzones across the cross-section of the fibers. The components may bearranged in any desired configuration, such as sheath-core,side-by-side, pie, island-in-the-sea, three island, bull's eye, orvarious other arrangements known in the art. Various methods for formingmulticomponent fibers are described in U.S. Pat. Nos. 4,789,592 toTaniguchi et al. and U.S. Pat. No. 5,336,552 to Strack, et al., U.S.Pat. No. 5,108,820 to Kaneko, et al., U.S. Pat. No. 4,795,668 to Kruege,et al., U.S. Pat. No. 5,382,400 to Pike, et al., U.S. Pat. No. 5,336,552to Strack, et al., and U.S. Pat. No. 6,200,669 to Marmon, et al., whichare incorporated herein in their entirety by reference thereto for allpurposes. Multicomponent fibers having various irregular shapes may alsobe formed, such as described in U.S. Pat. No. 5,277,976 to Hogle, etal., U.S. Pat. No. 5,162,074 to Hills, U.S. Pat. No. 5,466,410 to Hills,U.S. Pat. No. 5,069,970 to Largman, et al., and U.S. Pat. No. 5,057,368to Largman, et al., which are incorporated herein in their entirety byreference thereto for all purposes.

Although any combination of polymers may be used, the polymers of themulticomponent fibers are typically made from thermoplastic materialswith different glass transition or melting temperatures where a firstcomponent (e.g., sheath) melts at a temperature lower than a secondcomponent (e.g., core). Softening or melting of the first polymercomponent of the multicomponent fiber allows the multicomponent fibersto form a tacky skeletal structure, which upon cooling, stabilizes thefibrous structure. For example, the multicomponent fibers may have fromabout 5% to about 80%, and in some embodiments, from about 10% to about60% by weight of the low melting polymer. Further, the multicomponentfibers may have from about 95% to about 20%, and in some embodiments,from about 90% to about 40%, by weight of the high melting polymer. Someexamples of known sheath-core bicomponent fibers available from KoSaInc. of Charlotte, N.C. under the designations T-255 and T-256, both ofwhich use a polyolefin sheath, or T-254, which has a low meltco-polyester sheath. Still other known bicomponent fibers that may beused include those available from the Chisso Corporation of Moriyama,Japan or Fibervisions LLC of Wilmington, Del.

Fibers of any desired length may be employed, such as staple fibers,continuous fibers, etc. In one particular embodiment, for example,staple fibers may be used that have a fiber length in the range of fromabout 1 to about 150 millimeters, in some embodiments from about 5 toabout 50 millimeters, in some embodiments from about 10 to about 40millimeters, and in some embodiments, from about 10 to about 25millimeters. Although not required, carding techniques may be employedto form fibrous layers with staple fibers as is well known in the art.For example, fibers may be formed into a carded web by placing bales ofthe fibers into a picker that separates the fibers. Next, the fibers aresent through a combing or carding unit that further breaks apart andaligns the fibers in the machine direction so as to form a machinedirection-oriented fibrous nonwoven web. The carded web may then bebonded using known techniques to form a bonded carded nonwoven web.

If desired, the nonwoven web facing used to form the nonwoven compositemay have a multi-layer structure. Suitable multi-layered materials mayinclude, for instance, spunbond/meltblown/spunbond (SMS) laminates andspunbond/meltblown (SM) laminates. Various examples of suitable SMSlaminates are described in U.S. Pat. No. 4,041,203 to Brock et al.; U.S.Pat. No. 5,213,881 to Timmons, et al.; U.S. Pat. No. 5,464,688 toTimmons, et al.; U.S. Pat. No. 4,374,888 to Bornslaeger; U.S. Pat. No.5,169,706 to Collier, et al.; and U.S. Pat. No. 4,766,029 to Brock etal., which are incorporated herein in their entirety by referencethereto for all purposes. In addition, commercially available SMSlaminates may be obtained from Kimberly-Clark Corporation under thedesignations Spunguard® and Evolution®.

Another example of a multi-layered structure is a spunbond web producedon a multiple spin bank machine in which a spin bank deposits fibersover a layer of fibers deposited from a previous spin bank. Such anindividual spunbond nonwoven web may also be thought of as amulti-layered structure. In this situation, the various layers ofdeposited fibers in the nonwoven web may be the same, or they may bedifferent in basis weight and/or in terms of the composition, type,size, level of crimp, and/or shape of the fibers produced. As anotherexample, a single nonwoven web may be provided as two or moreindividually produced layers of a spunbond web, a carded web, etc.,which have been bonded together to form the nonwoven web. Theseindividually produced layers may differ in terms of production method,basis weight, composition, and fibers as discussed above.

A nonwoven web facing may also contain an additional fibrous componentsuch that it is considered a composite. For example, a nonwoven web maybe entangled with another fibrous component using any of a variety ofentanglement techniques known in the art (e.g., hydraulic, air,mechanical, etc.). In one embodiment, the nonwoven web is integrallyentangled with cellulosic fibers using hydraulic entanglement. A typicalhydraulic entangling process utilizes high pressure jet streams of waterto entangle fibers to form a highly entangled consolidated fibrousstructure, e.g., a nonwoven web. Hydraulically entangled nonwoven websof staple length and continuous fibers are disclosed, for example, inU.S. Patent No. 3,494,821 to Evans and U.S. Pat. No. 4,144,370 toBoulton, which are incorporated herein in their entirety by referencethereto for all purposes. Hydraulically entangled composite nonwovenwebs of a continuous fiber nonwoven web and a pulp layer are disclosed,for example, in U.S. Pat. No. 5,284,703 to Everhart, et al. and U.S.Pat. No. 6,315,864 to Anderson, et al., which are incorporated herein intheir entirety by reference thereto for all purposes. The fibrouscomponent of the composite may contain any desired amount of theresulting substrate. The fibrous component may contain greater thanabout 50% by weight of the composite, and in some embodiments, fromabout 60% to about 90% by weight of the composite. Likewise, thenonwoven web may contain less than about 50% by weight of the composite,and in some embodiments, from about 10% to about 40% by weight of thecomposite.

The nonwoven web facing may be necked in one or more directions prior tolamination to the film of the present invention. Suitable neckingtechniques are described in U.S. Pat. Nos. 5,336,545, 5,226,992,4,981,747 and 4,965,122 to Morman, as well as U.S. Patent ApplicationPublication No. 2004/0121687 to Morman, et al. Alternatively, thenonwoven web may remain relatively inextensible in a direction prior tolamination to the film. In such embodiments, the nonwoven web may beoptionally stretched in one or more directions subsequent to laminationto the elastic material.

Any of a variety of techniques may be employed to laminate the layerstogether, including adhesive bonding; thermal bonding; ultrasonicbonding; microwave bonding; extrusion coating; and so forth. In oneparticular embodiment, nip rolls apply a pressure to the precursorelastic material (e.g., film) and nonwoven facing(s) to thermally bondthe materials together. The rolls may be smooth and/or contain aplurality of raised bonding elements. Adhesives may also be employed,such as Rextac 2730 and 2723 available from Huntsman Polymers ofHouston, Tex., as well as adhesives available from Bostik Findley, Inc,of Wauwatosa, Wis. The type and basis weight of the adhesive used willbe determined on the elastic attributes desired in the final compositeand end use. For instance, the basis weight of the adhesive may be fromabout 1.0 to about 3.0 gsm. The adhesive may be applied to the nonwovenweb facings and/or the elastic material prior to lamination using anyknown technique, such as slot or melt spray adhesive systems. Duringlamination, the elastic material may in a stretched or relaxed conditiondepending on the desired properties of the resulting composite.

The lamination of the nonwoven web facing(s) and elastic material(s) mayoccur before and/or after crosslinking of the pentablock copolymer. Inone embodiment, for example, a precursor elastic material is initiallylaminated to a nonwoven web facing, and the resulting composite issubsequently subjected to electromagnetic radiation of a certain dosage.FIG. 1 schematically illustrates an exemplary process 10 for forming astretch-bonded composite in this manner. Initially, a thermoplasticprecursor layer 126 is stretched between a first set of nip rolls 132and 134, and a second set of nip rollers 136 and 138. To inducestretching, the second set of nip rolls may turn at a surface speedfaster than the first set of nip rolls. Nonwoven facing layers 24 and 28are also unwound from storage rolls 26 and 30 and combined with thestretched precursor layer 126 to form a composite 40 between nip rolls136 and 138, while the nonwoven layers 24 and 28 are relaxed. The layersmay be combined with the aid of an adhesive applied to the nonwovenlayers or the precursor layer, or with the aid of heat supplied fromroll 136 and/or 138.

After the composite 40 is formed, it then passes through a crosslinkingstation 128, thereby forming a composite that may be wound onto a roll44. The composite may be elastic in the machine direction, cross-machinedirection, or both. Although not shown, various additional potentialprocessing and/or finishing steps known in the art, such as slitting,treating, printing graphics, etc., may be performed without departingfrom the spirit and scope of the invention. For instance, the compositemay optionally be mechanically stretched in the cross-machine and/ormachine directions to enhance extensibility. In one embodiment, thecomposite may be coursed through two or more rolls that have grooves inthe CD and/or MD directions. Such grooved satellite/anvil rollarrangements are described in U.S. Patent Application Publication Nos.2004/0110442 to Rhim, et al. and 2006/0151914 to Gerndt, et al., whichare incorporated herein in their entirety by reference thereto for allpurposes. For instance, the composite may be coursed through two or morerolls that have grooves in the CD and/or MD directions. The groovedrolls may be constructed of steel or other hard material (such as a hardrubber). If desired, heat may be applied by any suitable method known inthe art, such as heated air, infrared heaters, heated nipped rolls, orpartial wrapping of the composite around one or more heated rolls orsteam canisters, etc. Heat may also be applied to the grooved rollsthemselves. It should also be understood that other grooved rollarrangement are equally suitable, such as two grooved rolls positionedimmediately adjacent to one another. Besides grooved rolls, othertechniques may also be used to mechanically stretch the composite in oneor more directions. For example, the composite may be passed through atenter frame that stretches the composite. Such tenter frames are wellknown in the art and described, for instance, in U.S. Patent ApplicationPublication No. 2004/0121687 to Morman, et al. The composite may also benecked. Suitable techniques necking techniques are described in U.S.Pat. Nos. 5,336,545, 5,226,992, 4,981,747 and 4,965,122 to Morman, aswell as U.S. Patent Application Publication No. 2004/0121687 to Morman,et al., all of which are incorporated herein in their entirety byreference thereto for all purposes.

The elastic material of the present invention may have a wide variety ofapplications, but is particularly useful as a component of an absorbentarticle. Although not required, a precursor elastic material may beincorporated into the absorbent article and subsequently crosslinked. Inthis manner, the material is not highly elastic prior to crosslinkingand is thus more dimensionally stable than highly elastic materials.This decreases the need for maintaining the material in a mechanicallystretched condition during attachment to other components of theabsorbent article and thus provides greater freedom in the location andmanner in which the components are attached together. Of course, theprecursor elastic material may also be crosslinked prior toincorporation into the absorbent article, such as described above andillustrated in FIG. 1.

The absorbent article normally includes a substantiallyliquid-impermeable layer (e.g., outer cover), a liquid-permeable layer(e.g., bodyside liner, surge layer, etc.), an absorbent core, andvarious other optional components. As is well known in the art, avariety of absorbent article components may possess elasticcharacteristics, such as waistbands, leg/cuff gasketing, ears, sidepanels, outer covers, and so forth. The crosslinked elastic material ofthe present invention may be employed for use in any of such components.Referring to FIG. 2, for example, one embodiment of a disposable diaper250 is shown that generally defines a front waist section 255, a rearwaist section 260, and an intermediate section 265 that interconnectsthe front and rear waist sections. The front and rear waist sections 255and 260 include the general portions of the diaper which are constructedto extend substantially over the wearer's front and rear abdominalregions, respectively, during use. The intermediate section 265 of thediaper includes the general portion of the diaper that is constructed toextend through the wearer's crotch region between the legs. Thus, theintermediate section 265 is an area where repeated liquid surgestypically occur in the diaper.

The diaper 250 includes, without limitation, an outer cover, orbacksheet 270, a liquid permeable bodyside liner, or topsheet, 275positioned in facing relation with the backsheet 270, and an absorbentcore body, or liquid retention structure, 280, such as an absorbent pad,which is located between the backsheet 270 and the topsheet 275. Thebacksheet 270 defines a length, or longitudinal direction 286, and awidth, or lateral direction 285 which, in the illustrated embodiment,coincide with the length and width of the diaper 250. The liquidretention structure 280 generally has a length and width that are lessthan the length and width of the backsheet 270, respectively. Thus,marginal portions of the diaper 250, such as marginal sections of thebacksheet 270 may extend past the terminal edges of the liquid retentionstructure 280. In the illustrated embodiments, for example, thebacksheet 270 extends outwardly beyond the terminal marginal edges ofthe liquid retention structure 280 to form side margins and end marginsof the diaper 250. The topsheet 275 is generally coextensive with thebacksheet 270 but may optionally cover an area that is larger or smallerthan the area of the backsheet 270, as desired.

To provide improved fit and to help reduce leakage of body exudates fromthe diaper 250, the diaper side margins and end margins may beelasticized with suitable elastic members, as further explained below.For example, as representatively illustrated in FIG. 2, the diaper 250may include leg/cuff gasketing 290 constructed to operably tension theside margins of the diaper 250 and closely fit around the legs of thewearer to reduce leakage and provide improved comfort and appearance.Waistbands 295 are employed that provide a resilient, comfortably closefit around the waist of the wearer. The crosslinked elastic material ofthe present invention is suitable for use as the leg/cuff gasketing 290and/or waistbands 295. Exemplary of such materials are composite sheetsthat either comprise or are adhered to the backsheet, such that elasticconstrictive forces are imparted to the backsheet 270.

As is known, fastening means, such as hook and loop fasteners, may beemployed to secure the diaper 250 on a wearer. Alternatively, otherfastening means, such as buttons, pins, snaps, adhesive tape fasteners,cohesives, fabric-and-loop fasteners, or the like, may be employed. Inthe illustrated embodiment, the diaper 250 includes a pair of sidepanels 300 (or ears) to which the fasteners 302, indicated as the hookportion of a hook and loop fastener, are attached. Generally, the sidepanels 300 are attached to the side edges of the diaper in one of thewaist sections 255, 260 and extend laterally outward therefrom. The sidepanels 300 may contain the elastic material of the present invention.Examples of absorbent articles that include side panels and selectivelyconfigured fastener tabs are described in PCT Patent Application WO95/16425 to Roessler; U.S. Pat. No. 5,399,219 to Roessler et al.; U.S.Pat. No. 5,540,796 to Fries; and U.S. Pat. No. 5,595,618 to Fries, eachof which is incorporated herein in its entirety by reference thereto forall purposes.

The diaper 250 may also include a surge management layer 305, locatedbetween the topsheet 275 and the liquid retention structure 280, torapidly accept fluid exudates and distribute the fluid exudates to theliquid retention structure 280 within the diaper 250. The diaper 250 mayfurther include a ventilation layer (not illustrated), also called aspacer, or spacer layer, located between the liquid retention structure280 and the backsheet 270 to insulate the backsheet 270 from the liquidretention structure 280 to reduce the dampness of the garment at theexterior surface of a breathable outer cover, or backsheet, 270.Examples of suitable surge management layers 305 are described in U.S.Pat. No. 5,486,166 to Bishop and U.S. Pat. No. 5,490,846 to Ellis.

As representatively illustrated in FIG. 2, the disposable diaper 250 mayalso include a pair of containment flaps 310 which are configured toprovide a barrier to the lateral flow of body exudates. The containmentflaps 310 may be located along the laterally opposed side edges of thediaper adjacent the side edges of the liquid retention structure 280.Each containment flap 310 typically defines an unattached edge that isconfigured to maintain an upright, perpendicular configuration in atleast the intermediate section 265 of the diaper 250 to form a sealagainst the wearer's body. The containment flaps 310 may extendlongitudinally along the entire length of the liquid retention structure280 or may only extend partially along the length of the liquidretention structure. When the containment flaps 310 are shorter inlength than the liquid retention structure 280, the containment flaps310 can be selectively positioned anywhere along the side edges of thediaper 250 in the intermediate section 265. Such containment flaps 310are generally well known to those skilled in the art. For example,suitable constructions and arrangements for containment flaps 310 aredescribed in U.S. Pat. No. 4,704,116 to Enloe.

The diaper 250 may be of various suitable shapes. For example, thediaper may have an overall rectangular shape, T-shape or anapproximately hour-glass shape. In the shown embodiment, the diaper 250has a generally I-shape. Other suitable components which may beincorporated on absorbent articles of the present invention may includewaist flaps and the like which are generally known to those skilled inthe art. Examples of diaper configurations suitable for use inconnection with the elastic materials of the present invention that mayinclude other components suitable for use on diapers are described inU.S. Pat. No. 4,798,603 to Meyer, et al.; U.S. Pat. No. 5,176,668 toBernardin; U.S. Pat. No. 5,176,672 to Bruemmer, et al.; U.S. Pat. No.5,192,606 to Proxmire, et al.; and U.S. Pat. No. 5,509,915 to Hanson, etal., which are incorporated herein in their entirety by referencethereto for all purposes.

The various regions and/or components of the diaper 250 may be assembledtogether using any known attachment mechanism, such as adhesive,ultrasonic, thermal bonds, etc. Suitable adhesives may include, forinstance, hot melt adhesives, pressure-sensitive adhesives, and soforth. When utilized, the adhesive may be applied as a uniform layer, apatterned layer, a sprayed pattern, or any of separate lines, swirls ordots. In the illustrated embodiment, for example, the topsheet 275 andbacksheet 270 may be assembled to each other and to the liquid retentionstructure 280 with lines of adhesive, such as a hot melt,pressure-sensitive adhesive. Similarly, other diaper components, such asthe leg/cuff gasketing 290, waistband 295, fastening members 302, andsurge layer 305 may be assembled into the article by employing theabove-identified attachment mechanisms.

Although various configurations of a diaper have been described above,it should be understood that other diaper and absorbent articleconfigurations are also included within the scope of the presentinvention. In addition, the present invention is by no means limited todiapers. In fact, any other absorbent article may be formed inaccordance with the present invention, including, but not limited to,other personal care absorbent articles, such as training pants,absorbent underpants, adult incontinence products, feminine hygieneproducts (e.g., sanitary napkins), swim wear, baby wipes, and so forth;medical absorbent articles, such as garments, fenestration materials,underpads, bandages, absorbent drapes, and medical wipes; food servicewipers; clothing articles; and so forth. Several examples of suchabsorbent articles are described in U.S. Pat. No. 5,649,916 to DiPalma.et al.; U.S. Pat. No. 6,110,158 to Kielpikowski; U.S. Pat. No. 6,663,611to Blaney, et al., which are incorporated herein in their entirety byreference thereto for all purposes. Still other suitable articles aredescribed in U.S. Patent Application Publication No. 2004/0060112 A1 toFell et al., as well as U.S. Pat. No. 4,886,512 to Damico et al.; U.S.Pat. No. 5,558,659 to Sherrod et al.; U.S. Pat. No. 6,888,044 to Fell etal.; and U.S. Pat. No. 6,511,465 to Freiburger et al., all of which areincorporated herein in their entirety by reference thereto for allpurposes. Of course, the elastic material is versatile and may also beincorporated into a wide variety of other types of articles. Forexample, the elastic material may be incorporated into a medicalgarment, such as gowns, caps, drapes, gloves, facemasks, etc.;industrial workwear garment, such as laboratory coats, coveralls, etc.;and so forth.

The present invention may be better understood with reference to thefollowing prophetic example.

Test Methods

Cycle Testing

The materials may be tested using a cyclical testing procedure todetermine load loss and percent set. For example, 1-cycle testing may beutilized to 200% defined elongation. For this test, the sample size maybe 3 inches in the cross-machine direction by 6 inches in the machinedirection. The grip size may be 3 inches in width. The grip separationmay be 4.5 inches. The samples may be loaded such that the machinedirection of the sample is in the vertical direction. A preload ofapproximately 10 to 15 grams may be set. The test may pull the sample to200% elongation at a speed of 20 inches per minute, and then immediately(without pause) return to zero at a speed of 20 inches per minute. Thetest reports percent set and percent hysteresis. The “percent set” isthe measure of the amount of the material stretched from its originallength after being cycled (the immediate deformation following the cycletest). The percent set is where the retraction curve of a cycle crossesthe elongation axis. The remaining strain after the removal of theapplied stress may be measured as the percent set. The hysteresis valueis the loss of energy during the cyclic loading. The testing may be doneon a MTS Corp. constant rate of extension tester 2/S with a Renew MTSmongoose box (controller) using TESTWORKS 4.07b software (MTS Corp, ofMinneapolis, Minn.). The tests may be conducted at ambient conditions.

Stress Relaxation

Stress relaxation is defined as the force required to hold a givenelongation constant over a period of time and is generally indicative ofthe dimensional stability of a material. Testing may be performed byclamping a test specimen (3″ in width) between the jaws of a Sintechextension tester at a 3″ grip to grip distance. The sample and the gripfixtures may be enclosed in an environmental chamber. The sample, afterclamping, may be equilibrated at 100° F. for 3 minutes. The sample maythen be elongated to a final constant elongation of 4.5 inches (50%elongation) at a cross-head displacement speed of 20 inches per minute.The load required to maintain the 50% elongation as a function of timemay be monitored. The slope of the stress curve and the percent loadloss may be reported. The percent load loss may be calculated bysubtracting the load at 12 hours from the initial load, dividing by theinitial load, and then multiplying the ratio by 100. The slope, which isconstant over the time period, is determined from a plot of log (load)versus log (time), or from the following equation:

$m = \frac{{- \Delta}\; {\log\left\lbrack \left( {{L(t)}/{L(0)}} \right\rbrack \right.}}{\Delta \; \log \; t}$

wherein,

m=the slope,

L(t)=load at a given time (t),

L(0)=starting load at t=0, and

t=time.

The testing may be done on a MTS Corp. constant rate of extension tester2/S with a Renew MTS mongoose box (controller) using TESTWORKS 4.07bsoftware (MTS Corp, of Minneapolis, Minn.).

Prophetic Example

A polymer blend may be formed from 90 wt. % of a B-S-B-S-B pentablockcopolymer and 10 wt. % of ESCOREZ® 5600 (Exxon Mobil Chemical Co.). Thepentablock copolymer may have a styrene content of 20-30 wt. %. ESCOREZ®5600 is a hydrocarbon resin. The blend may be introduced into the hopperof a Leistritz twin screw co-rotating multi-mode extruder (Model Mic27GL/40D) equipped with 27 mm screws at a 40:1 length:diameter ratio(“L/D”). The extruder may be an electrical resistance heated extruderwith water cooling, and contain 9 barrel heating sections and 2auxiliary heating sections. The extruder may be fitted with two“pineapple” mixing elements based on the principle of distributivemixing in the middle and end zones. The extruder may also be directlyfitted with a 10″ coat-hanger type film die that can be heated.Exemplary extrusion parameters are set forth below in Table 1:

TABLE 1 Extrusion Parameters Sample 1 2 Feed Rate (lb/hr) 8 8 ScrewSpeed (rpms) 300 300 Zone 1 (° C.) 150 150 Zone 2 (° C.) 150 150 Zone 3(° C.) 160 160 Zone 4 (° C.) 160 160 Zone 5 (° C.) 160 160 Zone 6 (° C.)160 160 Zone 7 (° C.) 160 160 Zone 8 (° C.) 160 160 Zone 9 (° C.) 160160 Zone 10 (° C.) 160 160 Zone 11 (° C.) 160 160 Torque (lbs) 29 30Winder Speed (ft/min) 8 13 Die Pressure (psi) 700 710

Once formed, the film samples may be subjected to electron beamradiation using Energy Sciences' pilot line equipment, which may beoperated at a voltage range from 80 kV to 200 kV, at a depth of 150microns, density of 1 g/cc, and a dosage range of 1-9 Mrads depending onspeed. The samples may have an approximate dimension of 10″×11″ and maybe placed on a carrier film that unwinds at one end and winds in theother end. Exposed samples may be collected and run a second or thirdtime depending on the dosage required. The materials may be tested forelastomeric performance as described above.

While the invention has been described in detail with respect to thespecific embodiments thereof, it will be appreciated that those skilledin the art, upon attaining an understanding of the foregoing, mayreadily conceive of alterations to, variations of, and equivalents tothese embodiments. Accordingly, the scope of the present inventionshould be assessed as that of the appended claims and any equivalentsthereto.

1. A nonwoven web material comprising an elastic component that includesa crosslinked network, the crosslinked network containing a pentablockcopolymer having at least two monoalkenyl aromatic midblocks positionedbetween conjugated diene endblocks.
 2. The nonwoven web material ofclaim 1, wherein the monoalkenyl aromatic midblocks include styrene or aderivative thereof and the conjugated diene endblocks include butadiene,isoprene, or a mixture thereof.
 3. The nonwoven web material of claim 1,wherein the pentablock copolymer is linear and has the general structure“ABABA”, wherein “A” refers to a conjugated diene block and “B” refersto a monoalkenyl aromatic block.
 4. The nonwoven web material of claim3, wherein the linear pentablock copolymer is selected from the groupconsisting of butadiene-styrene-butadiene-styrene-butadiene (“BSBSB”),isoprene-styrene-isoprene-styrene-isoprene (“ISISI”),butadiene-styrene-isoprene-styrene-butadiene (“BSISB”),butadiene-styrene-butadiene-styrene-isoprene (“BSBSI”),butadiene-styrene-isoprene-styrene-isoprene (“BSISI”),isoprene-styrene-butadiene-styrene-butadiene (“ISBSB”),isoprene-styrene-isoprene-styrene-butadiene (“ISISB”),isoprene-styrene-butadiene-styrene-isoprene (“ISBSI”), and mixturesthereof.
 5. The nonwoven web material of claim 1, wherein the pentablockcopolymer is branched and has the general structure “(A-B-A)_(n)”,wherein “A” refers to a conjugated diene block, “B” refers to amonoalkenyl aromatic block, “n” is equal to about 2 or more.
 6. Thenonwoven web material of claim 5, wherein “n” is from about 3 to about30.
 7. The nonwoven web material of claim 1, wherein the pentablockcopolymer constitutes about 10 wt. % or more of the elastic material. 8.The nonwoven web material of claim 1, wherein the pentablock copolymerconstitutes about 50 wt. % or more of the elastic material.
 9. Thenonwoven web material of claim 1, wherein the material is a compositethat contains a nonwoven web facing laminated to the elastic component.10. The nonwoven web material of claim 9, wherein the elastic componentis a film, strands, web, or a combination thereof.
 11. An absorbentarticle comprising an absorbent core positioned between a substantiallyliquid-impermeable layer and a liquid-permeable layer, the absorbentarticle comprising the nonwoven web material of claim
 1. 12. A methodfor forming a nonwoven composite, the method comprising: melt extrudingthe pentablock copolymer having at least two monoalkenyl aromaticmidblocks positioned between conjugated diene endblocks; forming aprecursor elastic material from the melt extruded pentablock copolymer;laminating the precursor elastic material to a nonwoven web facing; andcrosslinking the pentablock copolymer.
 13. The method of claim 12,wherein the precursor elastic material includes a film, strands, web, ora combination thereof.
 14. The method of claim 12, wherein thelaminating occurs prior to crosslinking of the pentablock copolymer. 15.The method of claim 12, wherein the laminating occurs after crosslinkingof the pentablock copolymer.
 16. The method of claim 12, whereincrosslinking is induced by electromagnetic radiation.
 17. The method ofclaim 16, wherein the electromagnetic radiation has a wavelength ofabout 100 nanometers or less.
 18. The method of claim 16, wherein thedosage of the electromagnetic radiation is from about 1 to about 30Megarads.
 19. The method of claim 16, wherein the dosage of theelectromagnetic radiation is from about 5 to about 15 Megarads.
 20. Themethod of claim 12, wherein the monoalkenyl aromatic midblock includesstyrene or a derivative thereof and the conjugated diene endblocksinclude butadiene, isoprene, or a mixture thereof.